Adjusting the VAZ 2108 carburetor: troubleshooting it yourself

Russian passenger cars VAZ 2108, 2109 and even the first “tens” were equipped with carburetors produced by the Dimitrovgrad Plant (DAAZ) under license from the famous European brand Solex. The units are quite unpretentious and reliable in operation, but still require periodic maintenance and adjustment. Most G8 owners can perform this procedure on their own if they carefully read all its intricacies. It is unacceptable to mindlessly interfere with the operation of the carburetor.

When adjustment is needed

Before you take a screwdriver and start turning the screws of the fuel unit, you need to understand one important point. It is as follows: adjusting the Solex carburetor is not a separate operation, but the final stage of the troubleshooting procedure or its scheduled cleaning. The only exception is if the settings were accidentally or unknowingly changed by you or someone else.

Solex carburetor - general view

The following signs indicate interruptions in the supply of the air-fuel mixture to the engine associated with Solex problems:

• the car began to stall at idle;
• fuel consumption has risen above normal and is accompanied by unstable operation of the power unit;
• a cold engine starts and immediately stalls, you have to make several attempts by manipulating the choke lever and the accelerator pedal;
• when you press the gas, a “failure” occurs, accelerating dynamics are completely absent;
• The car stalls while driving when you release the accelerator pedal while coasting.

Note. Unfortunately, the cause of the listed malfunctions is not always the carburetor. Problems with cold starts also arise when there is no compression in the cylinders, and the “culprits” for failures are often faulty spark plugs.

Wear of spark plugs also leads to increased gasoline consumption and the appearance of failures.

Point two: fixing not every problem ends with adjusting the fuel supply. The issue will be covered in more detail below, along with methods for repairing common breakdowns of the G8 carburetor. But in some cases you can’t do without adjustment:

• after removing or disassembling the Solex for the purpose of repair;
• upon successful cleaning or purging of the unit’s channels;
• after replacing rings or the entire piston group in a car engine;
• as a result of reconfiguring the timing in the ignition system, replacing high-voltage wires or installing new spark plugs.

Advice. Considering the low quality of fuel sold at many gas stations in Russia, it is recommended to remove the entire carburetor once every 20-25 thousand kilometers, disassemble it and thoroughly clean it with a compressor. After which you need to make adjustments.

Important points

• Before adjusting the carburetor, it is recommended to self-clean it. To do this, a special liquid for cleaning carburetors is poured into the gas tank, the engine starts and runs (the volume of liquid poured and the engine operating time are always indicated on the container with the cleaning liquid and depend on the specific brand). Sometimes this measure is enough to get rid of the above signs of carburetor malfunction and do without fine adjustments.
• If self-cleaning does not help, there is only one way out: you need to remove and wash the carburetor. For washing, both special liquids and ordinary kerosene are used. It is strictly not recommended to use brushes or fluffy rags to remove dirt. Hairs and lint remaining in the small holes of the carburetor can negate all efforts to clean it. The best option: thorough rinsing in a special liquid, and then blowing out all small holes with compressed air.
• Before removing the carburetor and cleaning the inside, it is recommended that the outside be thoroughly cleaned. Moreover, it is necessary to clean not only the carburetor itself, but also all the parts located next to it. Please be aware that any dirt left on adjacent parts may find its way into the clean carburetor when it is installed back into the engine. And if this happens, the entire cleaning procedure will have to start again.

In order for the carburetor to work correctly, attention should be paid not only to its adjustment, but also to cleaning. If any of these procedures are neglected, the carburetor will soon fail again. In addition, attention should be paid not only to the quality of gasoline, but also to the condition of the car’s air filter, since in some cases it is a worn filter that causes rapid contamination of the carburetor.

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Preparing tools and devices

If you intend to thoroughly clean the carburetor of your V8, then you will not be able to do it without a compressor. To blow out accumulated dirt from the channels, it is necessary to supply air at a pressure of at least 6 bar. The remaining tools are common ones found in every garage:

• 2 screwdrivers - Phillips and thin with a narrow flat slot;
• a set of small open-end wrenches - 8, 10, 13 mm;
• round nose pliers;
• rubber bulb (syringe);
• 2-3 wooden toothpicks;
• rags.

Compressor for carburetor purging

Note. It would be nice to have a tester or multimeter on hand to check the voltage. But if necessary, you can do without it.

Liquids for cleaning carburetor channels

A special product sold in aerosol cans (for example, from the ABRO brand) is excellent for cleaning channels. Do not use acetone or inorganic solvents, which corrode plastic parts, for cleaning. Buy new paper gaskets for DAAZ 2108 carburetors in advance (they will also fit the “nine”). You cannot buy or change jets, since the standard ones are designed for the entire service life of the machine, and fakes with large holes for fuel are often sold in repair kits.

This material will help you repair the carburetor mechanisms of VAZ 2106/2107 cars:

What to do with increased consumption

Before you tightly grasp the carburetor, be sure to make sure that the other systems are in good working order - the spark plugs are in working order, the high-voltage wires do not break through to ground, and there is compression in the engine cylinders (the minimum value for the VAZ 2108 is 11 Bar). Unscrew the spark plugs and check the condition of the electrodes.

Important. The color of the electrodes reflects the picture of the operation of the power unit. A black coating indicates that the mixture is over-rich, the proportion of gasoline in it is too high. White color indicates a lean mixture, the norm is a light brown tint.

Light brown is the correct color for the electrodes on the spark plugs

The most unpleasant problem is an increase in fuel consumption, which occurs for the following reasons:

• the economizer diaphragm is worn out;
• the main air jet or channels inside the unit are clogged;
• the needle valve, which limits the flow of fuel into the float chamber, does not hold;
• jets of unknown origin from a repair kit were installed.

Location of the economizer cover

Note. Listed here are problems that you can solve on your own. If the recommended measures do not have an effect, then the malfunction is more complex and you will have to contact a carburetor repair specialist to fix it.

To check the diaphragm, remove the air filter housing (the cover is secured with 3 10 mm nuts, the housing with 4 8 mm nuts). On the left wall of the carburetor in the direction of travel of the car, find a triangular economizer cap screwed with 3 screws, unscrew them with a Phillips screwdriver. Underneath there is a spring-loaded membrane that needs to be checked and replaced if necessary.

Removing the filter on the figure eight

You can read more about adjusting the carburetors of OKA cars here:

To eliminate other causes, you will have to remove the top cover of the Solex by disconnecting the starter cable and unscrewing the 5 fastening screws with a Phillips screwdriver. Then follow the instructions:

1. Unscrew the air jets, remembering where each one should be. Fuel jets are hidden under them in the wells; unscrew them with a thin screwdriver and pull them out with a toothpick. Blow through the calibrated holes thoroughly.
2. Using a blower, suck the gasoline out of the float chamber along with the dirt. Fill all channels and diffusers with the product from an aerosol can, wait for the time indicated on it and carefully blow out the carburetor without removing it from the car.
3. Take the removed cover of the unit, turn it with the floats up and try to blow into the fuel supply pipe, plugging the pressure release fitting with your finger. If air passes through, replace the needle valve as it will also allow gasoline to pass through unhindered.
4. If you replaced all the jets before increasing the flow rate, feel free to unscrew them and throw them away, and return the standard ones to their place.
5. Before assembly, make sure that the floats do not touch the walls of the chamber; if necessary, carefully bend them.
6. Reassemble the Solex in reverse order and begin adjusting.

To remove the top cover of the Solex you need to unscrew 5 screws

Reference. Oddly enough, with a lean mixture, gasoline consumption also increases. Since the car “does not pull” due to lack of fuel, you solve the problem by pressing the gas too hard, or even pulling the “choke”, half closing the air with the damper. Naturally, fuel is consumed beyond the norm.

Adjusting the fuel level in the Solex carburetor 21083, 2108, 21081

When the carburetor cover is removed, everything should look like this. The approximate fuel depth level should be approximately twenty-nine millimeters plus or minus one millimeter. The level must be measured immediately after the carburetor cap is removed. It is necessary to do this immediately only so that the gasoline does not evaporate. But you need to understand that the numbers given in the article are not an exact number, they are just an average value.

Sometimes those who repair cars use conditional values ​​in order to correctly set the fuel level. Such repairmen spontaneously control the tongue located on the float lever. They also sometimes pump up fuel to achieve the optimal level in the float chamber.

However, they are not guided by anything to do these actions. This approach has its place, but in order to achieve more accurate and accurate results, it is necessary to perform the usual standard fuel adjustment. At a minimum, standard adjustment is recommended by factories, and no special skills are required to carry it out. This adjustment is carried out in two simple steps on the carburetor cover turned upside down and positioned horizontally.

Photo of the location of carburetor parts

General diagram of the DAAZ 2108 unit

Jet placement diagram

Scheme for purging the cover channels

Fuel nozzles are removed with a wooden stick or toothpick

Replacing the needle valve

This is what the floats installed on the Solex lid look like

Alternative way

There is a simpler method for determining the correct position of the floats, which does not require measurements.

Place the carburetor cover on a flat table and look at the stampings made on the side surfaces. When the floats are in a normally adjusted position, these strips are parallel to the lid.

Then we lift the floats up and look at their bottom, which after lifting should be parallel to the surface of the lid. If necessary, adjust the position of the floats by bending the tongue.

After adjustment work, we assemble the carburetor.

Troubleshooting other problems

Among minor problems, the most common problems are idle speed. They are decided depending on the reason:

1. The electric valve that opens the idle jet does not work. Check the voltage supply to it with the ignition on, and then unscrew the valve and watch how it retracts the needle. If this does not happen, replace the part.
2. The idle jet is clogged. Again, unscrew the valve and blow through the calibrated hole.
3. The rubber o-ring on the valve has become loose. As a result, air leaks occur, causing the engine to operate unstably. Replace the seal.
4. The rubber ring sealing the idle channel is torn or weakened. It is put on a thin brass tube pressed into the carburetor body. To get to it, you need to remove the unit cover.
5. The channels supplying the fuel mixture for idling are clogged. The issue is resolved by washing and purging, as described in the previous section.

Idle valve with jet

Advice. If the idle speed disappears due to the fault of the electric valve during a trip, you can organize the fuel supply directly. Unscrew the element, remove the jet and remove the valve needle. Put it in place and calmly continue your journey, and upon arrival, replace it.

Replacing the trigger diaphragm

When the car stalls during a cold start, you need to change the trigger diaphragm. Due to the breakthrough, it does not retract the air damper, causing the engine to “suffocate.” The unit is located on the right side (in the direction of travel), its square cover is held on by 4 screws. Unscrew them and change the diaphragm.

Replacing the accelerator pump diaphragm

When you feel a “failure” when you press the accelerator and accelerate the car, your actions should be as follows:

1. Check the accelerator pump diaphragm, located under the cover on the left wall of the carburetor (in the direction of travel of the car). If it is torn, replace it.
2. Remove the air filter housing and the top cover of the Solex. Underneath it, look for nozzles built into the fuel supply diffusers. Pry them off with a screwdriver, pull them out and blow them out. Replace the rubber ring if it is torn.
3. Test how well the accelerator pump lever presses the diaphragm. If play is detected, change this lever.

The nozzles are removed using a screwdriver

The last malfunction lies in the electronic unit EPHH, which controls the operation of the electric valve. If the “eight” stalls when coasting in gear, then the reason is precisely this block. Changing it is not a problem; the price of this part is low.

Replacing the EPHH block

As a rule, after eliminating the listed problems, carburetor adjustment is not required. But if you notice a change in speed in one direction or another, then the settings can be slightly adjusted.

Diagnostics of VAZ 2108 carburetors - video

Checking the work done

After all the work has been completed, you will need to make sure that it is correct. To do this, you will need to turn the carburetor cap and make sure that the ball on the needle will not be sunk. If the stamping lines on the sides of the floats create parallelism with the cover, this will mean that the work was done correctly and everything is correct. If everything is done correctly, but there is no parallelism, then the problem will be a needle malfunction.

DIY adjustment instructions

The first adjustment of the Solex is performed during the assembly process. This is the installation of the trigger drive cable. Press the “choke” handle all the way, insert the cable into the hole in the lever, and clamp its casing on the bracket. Then secure the cable with a bolt when the damper is in the “fully open” position and check the operation of the mechanism.

1 — screw-regulator of the amount of mixture; 2 — quality screw; 3 - rubber ring; 4 - plug

2 screws are responsible for the fuel supply settings:

• a plastic handle installed on the right wall of the unit and regulating the amount of mixture;
• on the same side, at the end of the carburetor sole, there is a well where a screw is hidden - a mixture quality regulator, which is responsible for the ratio of air and fuel for idling.

The end of the starter cable must be secured with a bolt.

Important point. Please note that both propellers have virtually no effect on the operation of the engine while driving, since 90% of the fuel mixture goes into the cylinders directly through the diffusers, bypassing the idle system.

The operation of the VAZ 2108 carburetor is adjusted on a warm engine, so after assembly, start it and bring it to operating temperature. If the engine stalls during warm-up, add speed manually by slightly tightening the fuel quantity screw. Perform the settings in the following sequence:

1. Using a thin flat screwdriver, unscrew the quality screw until the engine speed stops increasing. Then tighten it half a turn.
2. Reduce engine speed to 100 rpm by turning the plastic quantity screw knob counterclockwise.
3. Achieve a crankshaft speed of 850 rpm by tightening the mixture quality screw.

Adjusting the mixture quality

If you have previously corrected minor problems, as a result of which the engine idle speed has become higher, then you do not need to touch the quality screw. Reduce them by turning the plastic handle, bringing them to the norm - 850 rpm.

Reference. Masters adjust VAZ 2108 carburetors using a special device - a gas analyzer that shows the level of carbon monoxide (CO) in the car's exhaust. At idle it should not exceed 1.5%, and at 2000 rpm - 2%. This is the best setup method, use it whenever possible.

How to adjust a Solex carburetor yourself

How to choose jets?

The selection of jets for Solex 21083 is made taking into account the engine size. Experts recommend starting the selection with a fuel nozzle for the first chamber. Having selected the desired sample, we select the corresponding air analogue for it. And then in the same order we select the jets for the second chamber. First you need to look for a factory carburetor designed for the size of your engine, remove the jets from it and take them as a reference point. Further selection of jets is made according to this principle. If you need to lean the mixture a little, choose a larger jet by one pitch. If you want to enrich it, use a smaller jet.

Emulsion hoses are assembled along with the jets. These tubes are designed to adjust the composition of the fuel mixture in accordance with engine speed. There are three types of tubes: 23, ZC and ZD. The first are used for Solex 21083 carburetors installed on transverse chisel engines. For the first chamber of carburetors of UZAM power units, ZD tubes are used, and for the second - ZC.